The Ford Barn

Ian in Mississauga · 08-08-2025, 10:18 AM

A few years ago I read about this test. Fiddle with the points to get a bright blue high voltage spark at least 1/4” long. Leave the the key on and the points closed or shorted. How long do I wait before checking the spark again? If the spark is the same then the coil and condenser are good.
TIA Ian

ModelA29 · 08-08-2025, 11:09 AM

miliseconds - at 2500 rpm the coil and condenser are firing 5,000 times a minute on a 4 cylinder engine or 83 times a second.

Jim Mason · 08-08-2025, 11:23 AM

Long enough to heat the coil/condenser. 5 minutes?

BButturff · 08-08-2025, 11:29 AM

I think it's important to test a condenser while it's warm. A condenser that tests good when cold might test bad when tested while it's warm. 120°F with a hair dryer should be warm enough.

alexiskai · 08-08-2025, 11:36 AM

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First, I would jump across the points with a wire so there’s no risk to the contacts. Then you want to be checking the coil temperature, either with an IR gun or by touch. It should be quite hot, in the 120-140° zone. An oil-filled coil will get hotter faster, so if you have an epoxy coil I would stop at the lower end of that range.

08-08-2025, 10:18 AM	#1
Ian in Mississauga Senior Member Join Date: May 2010 Posts: 140	Simple test for both condenser and coil A few years ago I read about this test. Fiddle with the points to get a bright blue high voltage spark at least 1/4” long. Leave the the key on and the points closed or shorted. How long do I wait before checking the spark again? If the spark is the same then the coil and condenser are good. TIA Ian

08-08-2025, 11:09 AM	#2
ModelA29 Senior Member Join Date: Sep 2022 Location: SoCal Posts: 1,152	Re: Simple test for both condenser and coil miliseconds - at 2500 rpm the coil and condenser are firing 5,000 times a minute on a 4 cylinder engine or 83 times a second.

08-08-2025, 11:29 AM	#4
BButturff Senior Member Join Date: Oct 2024 Location: The driftless area of SE Minnesota Posts: 117	Re: Simple test for both condenser and coil I think it's important to test a condenser while it's warm. A condenser that tests good when cold might test bad when tested while it's warm. 120°F with a hair dryer should be warm enough. __________________ _______________________ The other Bruce in Minnesota 1931 Model A Closed Cab (Budd) Pickup "Aurora" Model A Ford Club of America Lady Slipper A's

08-08-2025, 11:36 AM	#5
alexiskai Senior Member Join Date: Apr 2018 Location: Mebane NC Posts: 2,849	Re: Simple test for both condenser and coil Sponsored Links (Register now to hide all advertisements) First, I would jump across the points with a wire so there’s no risk to the contacts. Then you want to be checking the coil temperature, either with an IR gun or by touch. It should be quite hot, in the 120-140° zone. An oil-filled coil will get hotter faster, so if you have an epoxy coil I would stop at the lower end of that range.